Looks like the guy who flashed it has messed up. If your disc drive doesnt have the correct key, it will only play dvd's. He should still have your old firmware backed up, and so a copy of your key. Get him to redo it. If he hasn't, youre screwed, there is NO WAY of getting the key from your box, unless he has it, bad times....

Just Curious:
Did it work when he flashed it, and recently stopped working?
Did it never work after you got it flashed?
Did it give this error gradually before giving it consistently?
When was it flashed?